1. Field of the Invention
The present invention relates to a recording apparatus and a recording method for recording data to a rewritable recording medium, and a rewritable recording medium.
2. Description of the Related Art
Recently, various types of digital recording mediums have been developed. Conventional digital recording mediums include, for example, rewritable optical discs such as DVD-RW discs. DVD-RW discs usually allow data to be rewritten about 1000 times, and are used for recording video and audio and data for computer use.
DVD-RW discs adopt 8/16 modulation as a modulation rule for recording data. According to the 8/16 modulation, an 8-bit data symbol is converted into a 16-bit code word. There are a plurality of code words usable for one data symbol. In consideration of state information and a DSV (Digital Sum Value), it is determined which one of the plurality of code words is to be selected.
The DSV is obtained as follows. Each selected code word is converted by an NRZI (Non Return to Zero Inverted) system. Based on the resultant code, a CDS (Code Word Digital Sum) is obtained for each selected code word. The CDS's are added together to obtained the DSV.
The code word is selected also in consideration of the DSV of a code word subsequent to the code word which is now to be selected (current code word).
Demodulation is performed by converting the current code word (16 bits) into an 8-bit data symbol, referring to state information (2-bits) represented by the code word immediately subsequent to the current code word. For starting recording of data, the initial value of the state information is set to a prescribed fixed value, and the initial value of the DSV is set to 0.
The above-described technology has the following inconvenience. When the same data is recorded at the same position of an optical disc repeatedly, marks of the same pattern are recorded at the same position of the optical disc. Then, a portion of a recording thin film of the optical disc is melted and solidified a plurality of times by the marks being recorded, and another portion thereof is not melted or solidified by no mark being recorded. At a border area between the portion which is melted and solidified a plurality of times and the portion which is not melted or solidified, the recording thin film is likely to have defects. As a result of such defects being spread forward and rearward from the marks, the quality of a reproduction signal is deteriorated and thus the number of rewritable times of the optical disc decreases.